Introducing dislocations in ceramics by mechanical rolling: A first demonstration using SrTiO₃ crystal

It has long been known that dislocations can be used to tune the functional and mechanical properties of ceramics. However, introducing dislocations with controllable networks and densities into ceramics is difficult. In this study, a mechanical rolling technique was proposed to introduce dislocations into ceramics. Using a hard SiC ball with a diameter of 5 mm as a roller, plastic zones and dislocations were successfully produced in a SrTiO3 (STO) single crystal. The plastic zone area and dislocation densities were determined by the applied force (F) and number of rolling cycles. A force of 10 N produced a scalable plastic zone with an area of 140 mu m x 5000 mu m without crack formation after 100 rolling cycles. The dislocation density at the center of the plastic deformation zone can reach similar to 10(14) m(2), which is an order of magnitude higher than that achieved previously by others. Increasing the applied force increased the density of the introduced dislocations, for example, similar to 2 x 10(14) m(-2) under F = 30 and 35 N, however, lead to crack nucleation in the sample. The dislocations introduced significantly enhanced the mechanical properties of the STO crystal. The measured Vickers' hardness and fracture toughness increased by 55%-60% and 23%-24%, respectively, compared to the crystal before rolling. This method can serve as a robust technique for engineering dislocations in ceramics, fulfilling the requirements of dislocation-tuned mechanical and functional investigations.